TR-701FA is a new oxazolidinone derivative originally developed by Trius Therapeutics Inc. and has entered Phase III clinical trials, showing excellent antibacterial activity and low toxicity to broad-spectrum bacteria. The chemical name of TR-701FA is (R)-3-(4-(2-(2-methyltetrazol-5-yl)pyridine-5-yl)-3-fluorophenyl)-5-hydroxymethyl oxazolidin-2-onedihydrogenphosphate, and its chemical structural formula is as follows:

TR-701FA, tedizolid phosphate, is a pro-drug of the active moietytedizolid. Tedizolid is also known as TR-700 or torezolid. Its chemical name is (R)-3-(4-(2-(2-methyltetrazol-5-yl)pyridine-5-yl)-3-fluorophenyl)-5-hydroxymethyloxazolidin-2-one, and its chemical structural formula is as follows:

TR-701FA is activated by plasma esterase and plasma phosphatases in vivo and converts to the active moiety tedizolid, which has anti-bacterial function. TR-701FA has better solubility than tedizolid and it is stable in aqueous solution or acid solution; therefore, it is developed for injective or oral formulations.
Patent document WO2005/058886A1 disclosed Tedizolid and TR-701FA as well as their preparation methods.
Patent document WO2010/091131A1 disclosed a crystalline form of TR-701FA (for convenience, hereinafter referred to as “Form I”) and its preparation methods, and characterized the Form I with nuclear magnetic resonance hydrogen spectrum, X-ray powder diffraction pattern, Fourier-Raman spectrum, infrared spectrum, differential scanning calorimetry thermogram and dynamic moisture adsorption diagram.
In the present invention, it was discovered that the Form I of TR-701FA prepared by the method described in the Example 1 of WO2010/091131A1 has defects, such as low crystallinity, low solubility in water and high hygroscopicity. In order to satisfy the strict requirements for crystalline forms of active pharmaceutical ingredients in drug development, it is very important to develop novel crystalline forms of TR-701FA with more advantageous features.